Abstract: Lignocellulose is treated with an alkaline pretreatment liquor containing anthraquinone or other pretreatment agent in a continuous process in which the lignocellulose and pretreatment liquor flow countercurrently. The pretreatment agent is substantially soluble in the pretreatment liquor introduced into the pretreatment zone and is substantially insoluble in the pretreatment liquor withdrawn from the pretreatment zone, with the result that the pretreatment agent is effectively recycled within the pretreatment zone.

Abstract: By pretreating lignocellulose with an alkaline pretreatment liquor containing anthraquinone or a related compound, prior to alkaline digestion, a higher yield of pulp having a lower lignin content can be produced using less alkali. The pretreatment step is carried out under conditions that ensure survival of at least 50% of the anthraquinone or related compound in the pretreatment liquor, which is separated from the pretreated lignocellulose and reused to pretreat other lignocellulose.

Abstract: A wood chip stream capable of being selectively delaminated is produced by separating a mill-wood chip stream into respective first and second fractions on the basis of wood chip thickness. The first fraction consisting of wood chips having a predetermined thickness, is then pulped by conventional techniques. The wood chips in the second fraction are reduced to said predetermined thickness and are then selectively delaminated by compression means. After being subjected to selective delamination, the delaminated chips are pulped by conventional techniques. Accordingly, a high yield, uniform wood pulp having reduced pulp screen rejects is produced.